Just built a Tri-vibe from Slacker's Veroboard layout. First of all--credit where credit's due--ROG for the concept and design, and to Slacker for the Vero layout. Thanks, guys, for sharing your knowledge and efforts.
I haven't installed the board and off-board components in a box yet, just wired it up on a chair and plugged it in to test--basically a "breadboard" setup, running on 9V battery putting out 9.64 volts. Mostly, it works, but with a few bugs, and I could use some ideas if anybody can help:
1.) Getting a pretty strong "thump" that increases in rate with the rate pot, but goes away at lower levels of rate. Assume it's LFO related, but I would not describe it as a "tick", nor the whoosh-whoosh described earlier. I don't really want to do all the box drilling, installing, etc. before I de-bug it, but is it likely the thump comes from being totally unshielded? Would putting it into the (metal) box shield it and eliminate the thump?
2.) Both pots seem to have a lot of "wasted range" at both ends of the wiper travel. I did use an A taper pot for the Rate pot, and reversed leads as described in ROG's build notes. The 820K resistor stays the same, bridging #1 and 3 lugs on the pot, but does the jumper from lug 2 stay on lug 1, or go to lug 3 when the leads are reversed? Could this be some (all!!) of my problem? [ I do plan to eventually replace the Rate pot with the right one--a 500K C-taper, but from the build notes in ROG's article, I was expecting only reverse operation, and maybe some "bunching" up of the effect at one or the other end of the wiper travel--not a noise problem]
3.) I had to substitute 2 of the diodes, because I mis-ordered. I used 2 1N914 diodes I had on hand to sub for the 1N4149's specified. They seem to be indistinguishable, in fact, on line, the Fairchild data sheet is the same for both diodes, and I could find no mention of any significant difference. But--obviously the guys at ROG know what they're doing, I only occasionally think I know what I'm doing. . . (and am often wrong) Any chance this is my problem?
4.) I ran out of caps and had to use a disc cap for one of the 4n7 caps. I don't recall seeing any disc caps in anybody's build photos, and according to an article I read somewhere, disc caps can be microphonic. Although I thumped the cap several times with a finger, it did not make any noise, or alter the thump-thump-thump which is what I would expect a microphonic component to do (like tubes in my amp when they get microphonic). But again, any chance this is the problem? Why don't builders use disk caps in stompbox FX's?
5.) Post at or near the top of the page asks is there is a component(s) that can be changed to provide more depth. It might be part of what's already wrong with my build, but I'd like to add more depth, also, if there is a reasonable mod. that can be made to the circuit.
6.) Is there anything about going from the two TL-062's to the single TL-064 that I should check that might be part of the problem? (Other IC's used include NJM13600D and TL072, all from Small Bear)
I have not measured any voltages in the circuit, but can, if this would help someone point me in the right direction.
Thanks in advance for any help anyone can give me. This is really exciting--I'm looking forward to my new, quiet Tri-Vibe.
